A paint brush unloads paint relatively quickly where the end of the paint brush is not flagged. Flagged paint brushes are extremely expensive. A paint brush, even a flagged paint brush, leaves a trail because a paint brush is rectangular and paints like a boat running rearwardly in water or like a plow. Also, a paint brush has a relatively great amount of drag. A paint brush, even a flagged paint brush, leaves linear streaks (or linear bumps in the nature of ridges). Loading a paint brush is an art, known by few and practiced by even less. Loading a paint brush involves setting the paint up on the bristles above the flagging (or split ends or catches) without wiping the bristles on the rim of the can. Wiping the bristles on the side of the can to remove “excess” paint, practiced by most homeowners, is actually an unloading. In other words, the homeowner loads and unloads and then attempts to paint.
A paint roller leaves a trail on both sides and makes an orange peel effect. The high part of the bump does not dry well because it is too thick at such point. As one rolls, the roller lifts the paint from the surface because of the surface tension of the fiber, leaving a series of bumps.
A paint pad includes a foam backing and a layer of bristles glued onto the foam. The foam has some resiliency to permit a give to the layer of bristles as the layer of bristles run over the surface that is being painted. The foam further isolates the layer of bristles from the handle grasped by the user. The foam does not hold paint. The bristles unload paint instantly.
Paint may be sprayed with air, without air (airless), with air assist (air assist airless). Such painting produces the high/low (orange peel) effect. Airless is high volume, high pressure so one cannot do a fine finish. A wall has surface tension of its own. The surface tension is created by dirt and dust and residue on the wall. This surface tension has to be overcome for the sprayed paint to coat and stick to the wall. Further, the transfer efficiency of an air spray gun is about 25% to about 45%, of an airless spray gun is about 60%, of an air assist airless is about 75%, because with these methods much of the paint bounces off. With spray painting, everything in the room to be painted must be covered. With spraying, the end effect is a surface having a plurality of miniature nails sticking out from the surface. Such a rough surface immediately begins to collect dust and dirt. With spraying, a mask is best used.
Electrostatic (automotive) painting does not produce the high/low effect. Electrostatic painting leaves an almost perfectly smooth finish. However, one cannot ground sheetrock or wood or glass or plastic (without first providing an electrostatic coating onto the substrate).